The invention relates generally to a method and apparatus for measuring a variable in a fluid system and more particularly to a method and apparatus for measuring a fluid variable in a lubricant or coolant system and cleaning and undertaking a calibration check of the measurement device to ensure accurate measurement.
Most machine tools that remove metal, including automatic screw machines and computer controlled machining centers rely upon cooling and lubricating fluids applied to the machining site to improve tool life, enhance the surface finish of the machined region, increase cutting speeds and remove heat from the machining process to minimize distortion of the part and interference with or reduction of properties achieved by heat treatment.
Maintaining optimum concentrations and fluid characteristics of such cooling and lubricating fluids is desirable from the standpoints of maintaining optimum machining conditions, maximizing coolant and lubricant service life and therefore minimizing overall operating expense.
Numerous devices and methods have been developed to optimally use both cutting equipment and cooling and lubricating fluids. For example, U.S. Pat. No. 4,757,307 teaches a method of sensing the heat generated by a cutting tool to determine the condition of the tool.
U.S. Pat. No. 6,134,930 discloses a system wherein independent or distinct lubricating and cooling fluids are utilized to achieve distinct operational benefits.
Frequently, system operating conditions at the work site may be monitored and the information provided over land lines to a remote site where decisions regarding adjustment of fluid parameters are made and transmitted to the work site. Such a system is disclosed in U.S. Pat. No. 5,224,051.
In U.S. Pat. No. 6,336,362, a method and system for measuring and reporting the liquid level of tanks is taught. The system is particularly suited for detecting and reporting the level of liquid propane in industrial, commercial and residential tanks in order to prevent exhaustion of the gas supply at a particular site.
From the foregoing, it is apparent that monitoring and control systems relating to fluids, fluid quantity and fluid condition are diversified. Moreover, it is apparent that methods and apparatus addressing particular operational problems such as accurate measurement of a fluid variable such as pH, concentration, conductivity or temperature have not been fully developed. For example, many sensors are subject to fouling when exposed to coolants and lubricants and particularly so when the coolants and lubricants become contaminated. The present invention addresses and solves such problems.